The invention relates to the field of micro-electro-mechanical systems (MEMS), and in particular to MEMS using stored elastic potential energy for actuation in both switching directions, with the switch trigger provided by electrostatic forces.
In MEMS parallel plate and torsional actuators, the pull-in phenomenon has been effectively utilized as a switching mechanism for a number of applications. Pull-in is the term that describes the snapping together of parallel plate actuators due to a bifurcation point that arises from the nonlinearities of the system. Micro-electro-mechanical system (MEMS) switches based on parallel plate electrostatic actuators have demonstrated impressive performance in applications such as RF and low frequency electronic switching as well as optical switching.
However, these devices have not yet become significantly commercialized. One of the reasons for this is that these switches tend to have operating voltages higher than what is normally available from an integrated circuit. Voltage up-converters are therefore necessary for these devices to operate in a commercial application which adds cost, complexity, and power consumption. The high operating voltages are a result of the actuating voltage needing to exceed the high pull-in voltage of the parallel plate and torsional actuators. While some electrostatic MEMS switches have been designed for low (10-20V) pull-in (and actuation) voltages by decreasing the structure stiffness, this has so far only been done with a significant sacrifice in reliability and performance. There are other actuation techniques, such as thermal or magnetic, that operate with lower voltages, however these are significantly slower than electrostatic switches and also consume much more power.